It is well known to provide locks of the cylinder type in which more than one row of tumbler pins is provided. The most elementary form of cylinder lock is, of course, that in which only one row of tumbler pins is provided and the key for use with the lock has an edge which is indented in a somewhat sinuous fashion to various step values to which the tumblers extend when the key is fully inserted, thereby properly setting the tumbler pairs so that the lock can be operated. No fundamental difference exists with a lock in which two rows of tumblers are provided, the two rows being separated by 180.degree. with respect to the central axis of the lock. A further form of lock is known in which the tumblers protrude inwardly toward the key slot from the wider sides thereof so that they come in contact with the sides, rather than the edges, of the key and wherein the sides of the key are provided with identations or recesses into which the tumbler pins can extend. In locks of this type, the permutation of tumbler pins extends along a row, which may be staggered, such that the movement of the tumbler pins is angularly separated by 90.degree. from the edge-engaging tumblers, whether or not such edge-engaging tumblers actually exist.
In known flat keys of this type it has been found to be desirable to mill the recesses in an elongated form such that the recesses have a width substantially equal to the pin diameter and a length significantly greater than the pin diameter so that the pins extend into the recesses at points which are not precisely determinable by observation of the key. Thus, the centerlines of the tumblers are more effectively concealed. This leads to the further advantage that, due to having oblong recesses which are made by milling and which can have different lengths, depths and widths, unauthorized duplication of the key becomes somewhat more difficult than if drilled circular recesses are provided in the key shank or blade to receive cylindrical tumbler pins. In this connection, reference is made to Swiss Pat. No. 260,517.
It is conventional with flat keys of this general type to provide, in addition to the preferably cylindrical tumbler pins which laterally engage in oblong milled recesses of the 90.degree. lateral permutation, that is the so-called "lateral steps" on the flat sides of the key, other tumbler pins on the narrow side of the key which engage in drilled round recesses. The radial reception bores of the locking cylinder for the edge tumblers associated with these so-called "edge steps" generally have the same lengthwise spacing from the front of the cylinder as the reception bores for the lateral tumblers of the 90.degree. lateral permutation which are associated with the lateral steps. In other words, both sets of tumbler pins are arranged in the same grid in order to permit more rational tool utilization and, thereby, simpler manufacture. Thus, in the overall permutation, the bores for the lateral tumblers and the bores for the edge tumblers can be provided in the locking cylinder in common planes which are perpendicular to the cylinder axis. Thus, the recesses made on the flat key as lateral and edge steps are arranged in pairs with the same longitudinal spacings of the center positions of the associated tumbler pins from the key stop, which is commonly the front face of the lock rotor. In this case, the lateral steps of the flat key only assume the function of identification of key and locking cylinder because they are extended in the longitudinal direction of the key on either side from the center position of the associated tumbler, whereas the edge steps made in the form of countersunk holes fulfill the function of limiting longitudinal pulling of the inserted key together with that of identification.
However, with these known flat keys there is the disadvantage that longitudinal movement of the key can take place after the turning motion of the key has commenced, in which case the tumbler ends engaged in the edge steps of the key begin to move radially by ascending the 45.degree. sides of the conical edge bores and are raised, with respect to the axis, until the head thereof strikes against the wall of the rotor reception bore in the stator, whereas the tumbler pins of the 90.degree. lateral permutation milled into the lateral steps of the key extended on either side remain on the basis of their respective elongated recesses. Thus, during rotation of the rotor the tumbler pins of the edge tumblers can penetrate the stator bores of the 90.degree. lateral tumblers as the rotor is rotated to a position in which the tumblers become approximately aligned with the next set of stator bores. These pins can then engage in the stator bores so that further rotation of the rotor and key is prevented.
This so-called "hanging up" of tumbler pins of the additional permutation in the "extraneous" stator bores can, in principle, also occur for the same reasons if on the flat sides of the key in addition to the oblong milled recesses of the 90.degree. lateral permutation, additional recesses are provided for the tumbler pins of a 45.degree. additional permutation inclined by an angle of 45.degree. relative to the key side face. In this arrangement, the radial reception bores of the locking cylinder for the 90.degree. lateral tumblers and those for the tumblers of the 45.degree. additional permutation are arranged pairwise in common planes perpendicular to the cylinder axis. The reason for this is that if the key is pulled shortly after the start of turning of the key, the tumbler pins of one row of steps of the 45.degree. additiional permutation can "hang up" in a passing row of stator bores of the 90.degree. lateral tumblers when the rotor is rotated to a position of 45.degree. from its initial position. This is because the tumbler pins of the 45.degree. lateral permutation which exercise the function of limiting the longitudinal travel of the key are displaced outwardly during rotor rotation by the side pressure (in a tangential direction) of the conically drilled recesses of the 45.degree. permutation, which force is exerted as a result of pulling of the key against the conical pin tips. Thus, the pin heads engage under pressure against the wall of the rotor reception bore and, consequently, on further rotation of the rotor tend to "wait" to engage in passing extraneous stator bores.
A further disadvantage of the known flat key in which the additional recesses are constructed as countersunk holes, regardless of whether these are constructed only as edge steps or also as 45.degree. lateral steps, where the additional recesses assume the function of limiting longitudinal pulling of the inserted key, is that through premature pulling on the key during rotor rotation and also through any hanging up in extraneous stator bores, the associated tumbler pins are subject to much more wear than the tumbler pins of the 90.degree. lateral permutation which engage only in the lateral steps of the flat key extended on either side and only performing an identification function between the key and the locking cylinder. This disadvantage is particularly important because it is the weakest type of tumbler which must assume the longitudinal pull-limiting function in that the tumblers of the additional permutations often have a smaller diameter for structural or space-saving reasons than the tumblers of the 90.degree. lateral permutation.